On 25 February 2013, she reached her best singles ranking of world number 102. On 18 June 2012, she peaked at world number 151 in the doubles rankings. Koehler made her debut on the International Tennis Federation Women"s Circuit at the age of 14 at a $10,000 event in Braga.
Having qualified for the main draw, she lost her first match to Catarina Ferreira.
She made her Women's Tennis Association tour main draw debut at the 2009 Estoril Open. Having been awarded a wild card, she played world number 77 Kristina Barrois in the first round, losing in straight sets.